IEEE 802.15 describes a communication architecture, which may enable communicating devices (DEVs) to communicate via wireless personal area networks (WPANs). Many DEVs utilized in WPANs are small or handheld devices, such as personal digital assistants, portable computers, or consumer electronics devices such as digital video recorders or set top boxes. IEEE 802.15 is a short-range wireless communications standard that enables connection between consumer and computer equipment while eliminating wires. IEEE 802.15 WPAN DEVs may utilize frequencies in the 57 GHz to 66 GHz range for communication.
A plurality of communicating DEVs in a WPAN environment may comprise a network known as a piconet. One of the DEVs in a piconet may function as a piconet coordinator (or controller), or PNC. The PNC may provide overall coordination for the communication between DEVs in a piconet. The piconet may comprise the PNC and DEVs, which are associated with the PNC.
Communications between communicating DEVs in a WPAN may occur within time intervals referred to as superframes. The superframe may comprise a plurality of segments. In a first superframe segment, the PNC may transmit one or more beacon frames. The beacon frame may enable recipient DEVs to identify the PNC. The beacon frame may also enable recipient DEVs to identify other DEVs, which are currently associated with PNC within the piconet. In addition, a beacon frame may indicate time durations within the current superframe during which assigned DEVs may transmit and/or receive signals via a wireless communication medium. These time durations may be referred to as time slots. The time slot assignments may be in response to requests received from the DEVs during one or more previous superframes.
A second superframe segment may comprise a contention access period (CAP). The starting time instant and time duration of the CAP may be communicated within the preceding beacon frame. During the CAP, the DEVs may respond to the beacon frames by communicating with the PNC to establish an association within the piconet. Associations established during a current superframe may be reported via beacon frames in one or more subsequent superframes.
The DEVs within the piconet may also utilize the CAP to communicate data to other DEVs. Communicating DEVs may attempt to gain access to the wireless communication medium before attempting to transmit data. The collision sense multiple access with collision avoidance (CSMA/CA) protocol is typically utilized by communicating devices for wireless medium access. During the CAP, a DEV seeking medium access, an originating DEV, may transmit a request to send (RTS) frame. The RTS frame may be addressed to a destination DEV but the RTS frame may be received by other DEVs. The destination DEV may respond to the RTS frame by transmitting a clear to send (CTS) frame. The originating DEV and destination DEV may subsequently commence communication via the wireless medium. The communications may, for example, involve the transmission of data frames between the originating DEV and the destination DEV. Direct communications between an originating DEV and a destination DEV during the CAP are typically intermittent communications, which comprise relatively short time durations. In accordance with the CSMA/CA protocol, other DEVs that receive the RTS frame transmitted by the originating DEV may refrain from transmitting signals via the wireless medium during these communications. When an originating DEV seeks to reserve access to the wireless medium for longer time durations, the originating DEV may transmit an RTS frame to the PNC during the CAP. The PNC may respond to the originating RTS frame by sending an acknowledgment frame that comprises a time allocation slot.
A third superframe segment may comprise a channel time allocation (CTA) period. The CTA period may comprise one or more CTA time slots. During the CTA period, the PNC may assign and/or schedule a set of CTA time slots to one or more DEVs within the piconet. The PNC may communicate a time allocation slot to an assigned DEV during the CAP that identifies a specific CTA time slot. During the assigned CTA time slot the assigned DEV may be granted reserved access to the wireless communication medium. The assigned DEV may utilize the assigned CTA time slot to engage in communications with one or more destination DEVs. Other DEVs, which are not engaged in communications with the originating DEV, may refrain from transmitting signals via the wireless communication medium during the assigned CTA time slot. In conventional piconet systems, an individual CTA time slot is assigned to a single DEV. Thus, a single DEV may transmit signals via the wireless communication medium during a given CTA time slot.
The CTA period may also comprise a management CTA (MCTA) period. During the MCTA period, DEVs may request CTA time slot assignments from the PNC. The PNC may respond to CTA time slot allocation requests received in the current superframe by making CTA time slot assignments for one or more subsequent superframes. The time slot assignments may be reported via beacon frames transmitted during the respective subsequent superframes.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with some aspects of the present invention as set forth in the remainder of the present application with reference to the drawings.